Temperature compensated time delay relay



June 14, 1966 A. L. BASTIAN TEMPERATURE coMPENsATED TIME DELAY RELAY Filed Aug. 16, 1963 INVENTOR.

A 7' TOR/VE Y N m s A E L w m R A United States Patent 0 3,256,410 y TEMPERATURE COMPENSATED TIME DELAY RELAY Arthur L. Bastian, Hackensack, NJ., assignor to Branson Corporation, Whippany, NJ., a corporation of Dela- This invention relates to time-delay relays and more particularly to an electrical time-delay relay of improved construction.

Time-delay relays of the class to which this invention is directed operate on the principle of the thermal expansion of an actuating member to effect the actua-tion of electrical contacts, thereby to provide an alarm or control function. The actuation of the electrical contacts takes place a predetermined time interval after heat has been applied to, or removed from, the actuating member through the medium of an electrical heating means associated therewith. Essentially, such relays are compensated for changes in ambient temperature in order to provide the same time-delay action over the entire ambient temperature range within which the relay is expected to operate. Generally, this is accomplished by incorporating, within the relay, a compensating member having the same temperature coefficient of expansion as the contact-actuating member rbut thermally isolated therefrom, whereby the relative spacing between the cooperating electrical contacts remains constant throughout .the normal range of ambient temperature changes.

An object of this invention is the provision of an elec- -trical time-delay relay of simple, economical construction and which lends itself to miniaturization.

A11 object of this invention is the provision of an electrical time-delay relay of small size and having a high degree of thermal isolation between the contact-actuating mechanism and the ambient temperature compensator, thereby increasing the operating efficiency.

-An object of this invention is the provision of a timedelay relay wherein the ambient temperature compen- 'sating means constitutes a part of the relay housing whereby the entire inner volume of the housing is available for other components, thus increasing the volumetric efficiency of the design and aiding in miniaturization of the relay.

An object of this invention is the provision of a timedelay relay having a set of cooperatingelectrical contacts, one contact being fixed and the other contact being carried by a cantilevered mechanism, an actuating member having an electrical heater associated therewith, and means effecting a flexing of the cantilever mechanism in response to the thermal expansion of the actuating member.

These and other objects and advantages of the invention will become apparent from the following description when taken with the accompanying drawings. It will be understood, however, that the drawings are fo-r purposes of illustration and are not to be construed as defining the scope or limits of the invention, reference being had for the latter purpose lto the claims appended hereto.

In the drawings wherein like refe-rence characters denote like parts in the several views:

FIGURE 1 is an isometric View showing a time-delay relay made in accordance with this invention;

FIGURE 2 is an end view showing the front of the relay;

FIGURE 3 is a central, longitudinal, cross-sectional view of the relay, with the heater coil omitted; and

FIGURE 4 is an isometric View showing another construction of the movable contact assembly.

Reference, now, is made to FIGURES 1 and 2 wherein Patented June 14, 1966 there is shown a base 10 made of a suitable metal and having a plurality of pins extending therethrough, the front row pins 11-14 being visible in this view of FIG- URE 1 and one of the rear pins 11' being shown in dotted lines. Each pin is electrically insulated from the 'base by means of associated glass inserts 15 thereby forming a header. Positioned on the upper surface of the base is a thin sheet 16 of insulation, preferably mica, which sheet is punched to provide clearance holes for the pins.

The yactuator 17, comprising a generally C-shaped block of suitable metal, has its long leg 18 resting upon the mica sheet and welded to the transversely-aligned set of pins 11, 11'. A heater coil C, here shown wound around the base portion of the actuator, has vone lead soldered to the pin 13 and the other lead soldered tothe transversely-aligned rear pin which is not visible in the drawing. The other end 19, of the actuator, has a reduced-Width portion spaced a predetermined distance from the upper surface of the l,base 10. It is here pointed out that lthe actuator 17 and the base 10 are made of a metal having a high temperature coefficient of expansion, such as stainless steel, and the physical proportions of these members are matched so thattheir axial expansion and contraction will be equal over a fairly wide range of ambient temperature variations. Consequently, the base 10 serves not only as a support for the Various corn- -ponents 'but also functions as a temperature compensator. Also, although the actuator 17 is4 supported directly on the base, it is electrically insulated therefrom by the mica sheet and the glass inserts. Because of the low thermal conductivity of the mica and glass, the actuator effectively is thermally insulated from the base. This is an important consideration in devices of this type since the difference in temperature between the actuator and the compensator (base 10), brought about by current flowing in the heater coil, effects the actuation of the electrical contacts, as willl 'be described hereinbelow.

The pin 12 is relatively long, is offset inwardly and has a cylinder 20 secured thereto, said cylindei being rnade of a material having good electrical contact characteristics, such as silver or platinum-iridium. This constitutes the stationary contact of the relay. The movable contact comprises a button 21, of similar material, and riveted to the ends of the leafs, or fingers 22, 23. These fingers are made of a material having a very low temperature coefficient of expansion, such as, for example, Invar. The end portions of the fingers, which carry the contact 21, are coplanar and welded together, whereas the other end portions are spaced apart. The end of the upper finger 22 is welded to the face of the short leg 19, of the actuator, and the corresponding end ofthe lower finger 23 is welded to the surface of a cross bar 24 having an integral adjustment lever 25 extending therefrom.

The opposed ends of the cross bar 24 are provided with semi-circular vertical channels accommodating the transversely-aligned set of pins 14 and 14 (see FIGURE 2). The cross bar is welded to such fingers but its lower surface is spaced somewhat from .the mica sheet 16 for purposes which will be explained hereinbelow. A thin, flat spring 26 is welded to the cross bar and to the actuator leg 19, thereby providing a predetermined, accurate spacing between these members. This flat spring essentially is rigid to vertical and transverse loading lying in the plane of the spring but is flexible to longitudinal motion of either of the attached members in a direction normal to the plane of the spring. It will be apparent, therefore, that the flat spring maintains the spacing between the actuator end 19 and the cross bar 24 without resistance to the axial, thermal expansion of the `actuator 17 relative to the cross bar 14.

In the illustrated construction, the stationary contact 2t) normally is spaced from the movable contact 21. The initial, preset spacing between these contacts is maintained throughout a wide `range of ambient temperature variations, since both the actuator 17 and the base 10 expanded equally. When the heater c-oil is energized, the rapid transfer of. heat to the actuator causes the latter to expand thereby applying tension to the cantilever mechanism comprising the anchored fingers 22, 23. This causes the fingers to fiex thereby moving the movable contact 21 toward the fixed contact 22. The time delay between the moment of application of heat to the actuator and the closure of the contacts depends upon the design parameters of the particular relay. Electrical connection of the contacts to an external circuit is made by means of the pin 12 (carrying the stationary contact) and either of the two pins connected to the cross bar.

As stated hereinabove, 4the adjustment lever 25 is integral with the cross bar 24, which cross bar is welded t-o the transversely aligned pins but spaced from the mica sheet. Such pins effectively serve as fulcrum points for the lever. With specific reference to FIGURE 1, it will be seen that raising the free end of the relatively thick lever 25 will forcefully bend the two supporting pins to the right thereby applying tension to the lower finger 23 and causing the movable contact 21 to move further away from the fixed contact. Thus, the lever 25 provides a means for adjusting the ini-tial spacing between the two electrical contacts.

Reference is now made to FIGURE 3, which is a longitudinal, cross-sectional view of the relay shown in FIG- URE l but with the heater coil omitted. This view shows the integral adjustment lever 25 and the cross bar 24, the latter being spaced from the mica sheet 16. An adjusting screw 27 is -threaded into a hole provided in the base and extends through a clearance hole formed in the mica sheet. A rivet 28 has a shank passing through a clearance hole provided in fthe lever 25 and force-fitted into an axial bore provided in the screw. A slight clearance is provided between the end of the screw and the lever whereby the screw may be rotated to effect an upward or downward displacement of the lever. An upward lever displacement results in an increase in the spacing between the contacts 20, 21, whereas a downward lever displacement results in a decrease in such spacing. Since the two pins to which the cross bar 24 is attached (pins 14 and 14 visible in FIGURE 2) are relatively heavy, the lever 25 will remain in the adjusted position under conditions of high shock.

When the relay is intended `for service under conditions of high vibration, the cantilever mechanism can be modified as shown in FIGURE 4. Here, the upper finger 22' includes a wider central portion which is bent along 1ongitudinal lines to form depending side edges, which edges are spaced from the proximate sides of the lower finger 23.

A time-delay relay, made in accordance with this invention, can be made in a very small overall size and can be hermeti'cally sealed. A simple, rectangular, cup-like case (as shown by the dotted lines 30 in FIGURE 1) can be positioned with its open end resting upon the peripheral ledge formed in the base and the case and base made integral by soldering.

The relay shown in FIGURE 1 is of the normallyopen type, that is, the two contacts are spaced apart at ambient temperatures and becomes engaged a predetermined time nterval after the heater is energized. With the fixed contact 20 positioned beneath the fingers 22, 23 and in normal engagement with the lower surface of the movable contact 21, a normally-closed contact arrangement is provided. Both such arrangements can be utilized to provide a relay of the single-pole, double-throw class.

Various other changes and modifications can be made in the illustrated and described construction. The heater element may take the form of a resistor positioned within 4 a recess provided inthe actuator. The actuator can have a variety of shapes and can be perforated with holes to reduce the operating time constant of the relay. Also, the base and the actuator can be made of different metals and unequal axial lengths, provided the temperature coefficients of expansion are chosen to provide the desired ambient temperature compensation. The cantilever mechanism can be spring-biased in one or the other directions to effectuate a desired operating characteristic. These and lother changes and modifications may be made without departing from the scope and spirit of the invention as recited in the following claims.

I claim:

1. An electrical time-delay relay comprising,

(a) abase made of a met-al having a relatively high.

coefiicientv lof thermal expansion,

(b) a generally C-shaped actuator made of a metal having :a rela-tively high temperature coeficient 'of expansion Iand carried by said base,said actuator having an elongated base portion joined to legs of unequal length,

(c) a pair of diver-ging -fingers made of a metal having a negligible temperature coefiicient of expansion, one end of the one finger being secured to the shorter leg of the actuator, the corresponding end of the other finger being secured to said base, and the free ends of the fingers being joined together,

(d) a movable contact secured to the joined ends of the fingers,

(e) a cooperating stationary contact carried by the base and insulated therefrom, and

(f) a heater in heat-transfer relation to the base portion of the actuator.

2. The Iinvention as recited in claim 1, including thermal' insulation means disposed between the longer leg of the actuator and the base.

3. The -invention as recited in claim 1, wherein one of said fingers 4includes side walls offset in the direction of the other finger and spaced from the side edges thereof.

4. A time-delay relay comprising,

(a) a base made of a metal having a relatively high coefficient of thermal expansion,

(b) a plurality of sets of contact pins extending through the base and electrically insulated therefrom,

(c) a generally C-shaped actuator made of a metal having a relatively high coefficient of thermal expan- .sion one leg of said actuator being secured to a set of pins at one end of the base and the other leg being 'spaced from the base,

(d) a cross-bar member secured lto a set of pins at the other end of the base, said member having a lower surface spaced from the base and an upper surface spaced from said other leg of the actuator,

(e) a pair of fingers in the form of fiat strips of metal having a substantially zero coefiicient of thermal expansion, one end of the `one strip being secured to the :said `other leg of the actuator, one end `ot the other strip being secured to the said cross-bar member, yand the free ends of the strip being joined together,

(f) a movable contact carried by the joined ends of the said strips,

(g) Ia cooperating stationary contact carried by a pin intermediate of said end sets of pins, and

(h) ra heater element in heat-transfer relation with said actuator, said heater element being connected Ito a third `set of pins.

5. The invention as recited in claim 4, including an adjustment lever integral with said cross-bar member and extending in spaced-relation to the said fingers and the base, and adjustable means .for defiecting the said adjustment lever relative to said base, thereby to bend the pins secu-red to the cross-bar member for the purpose yof ad- Ajustirlg the relative spacing between the movable and fixed contacts.

3,256,410 5 6 6. The invention as recited in claim 4, including a dat 4 References Cited bythe Examiner leaf spring secured to the said cross-bar member and the UNITED STATES PATENTS said other leg of the actuator, said spring maintaining the spacing between the cross-bar member and the sa-id 2 ewls leg of the actuator while permitting longitudinal expan- 5 yers l sion of the actuator relative to the base. 2937255 5/1960 Ulanet 20o-137 7. The invention as recited in claim 5, wherein the 3056871 10/1962 Broekhuysen Zool base is rectangular and has the same coecient of ther- FOREIGN PATENTS mal expansion as the said actuator. 159,478 8/ 1922 Great Britain.

8. The invention as recited in claim 5, wherein the 10 said base is provided with a peripheral ledge, -in combina- BERNARD A' GILHEANY Prmary Exammer' tion with a cup-like case `supported by the said ledge. L. W. WRIGHT, Assistant Examiner. 

1. AN ELECTRICAL TIME-DELAY RELAY COMPRISING, (A) A BASE MADE OF A METAL HAVING A RELATIVELY HIGH COEFFICIENT OF THERMAL EXPANSION, (B) A GENERALLY C-SHAPED ACTUATOR MADE OF A METAL HAVING A RELATIVELY HIGH TEMPERATRE COEFFICIENT OF EXPANSION AND CARRIED BY SAID BASE, SAID ACTUATOR HAVING AN ELONGATED BASE PORTION JOINED TO LEGS OF UNEQUAL LENGTH, (C) A PAIR OF DIVERGING FINGERS MADE OF A METAL HAVING A NEGLIGIBLE TEMPERATURE COEFFICIENT OF EXPANSION, ONE END OF THE ONE FINGER BEING SECURED TO THE SHORTER LEG OF THE ACTUATOR, THE CORRESPONDING END OF THE OTHER FINGER BEING SECURED TO SAID BASE, AND THE FREE ENDS OF THE FINGERS BEING JOINED TOGETHER, (D) A MOVABLE CONTACT SECURED TO THE JOINED ENDS OF THE FINGERS, (E) A COOPERATING STATIONARY CONTACT CARRIED BY THE BASE AND INSULATED THEREFROM, AND (F) A HEATER IN HEAT-TRANSFER RELATION TO THE BASE PORTION OF THE ACTUATOR. 